Add enough test cases to achieve at least 70% code coverage.
This means that, when you run yarn test (which should execute jest --coverage),
then the % Stmts entry for All files should be greater or equal than 70.0.
What kind of tests to add is up to you.
Create an account on Heroku (or any other cloud-provider you prefer), and deploy this
application on it.
In case of Heroku, remember to have a .gitignored file, and possibly configure
Heroku settings via the engines entry in the package.json configuration file.
Solutions to this exercise can be found under the exercise-solutions folder.